69 research outputs found
Multipole moments in Kaluza-Klein theories
This paper contains discussion of the problem of motion of extended i.e. non
point test bodies in multidimensional space. Extended bodies are described in
terms of so called multipole moments. Using approximated form of equations of
motion for extended bodies deviation from geodesic motion is derived. Results
are applied to special form of space-time.Comment: 11 pages, AMS-TeX, few misprints corrected, to appear in Classical
and Quantum Gravit
An axiomatic approach to electromagnetic and gravitational radiation reaction of particles in curved spacetime
The problem of determining the electromagnetic and gravitational
``self-force'' on a particle in a curved spacetime is investigated using an
axiomatic approach. In the electromagnetic case, our key postulate is a
``comparison axiom'', which states that whenever two particles of the same
charge have the same magnitude of acceleration, the difference in their
self-force is given by the ordinary Lorentz force of the difference in their
(suitably compared) electromagnetic fields. We thereby derive an expression for
the electromagnetic self-force which agrees with that of DeWitt and Brehme as
corrected by Hobbs. Despite several important differences, our analysis of the
gravitational self-force proceeds in close parallel with the electromagnetic
case. In the gravitational case, our final expression for the (reduced order)
equations of motion shows that the deviation from geodesic motion arises
entirely from a ``tail term'', in agreement with recent results of Mino et al.
Throughout the paper, we take the view that ``point particles'' do not make
sense as fundamental objects, but that ``point particle equations of motion''
do make sense as means of encoding information about the motion of an extended
body in the limit where not only the size but also the charge and mass of the
body go to zero at a suitable rate. Plausibility arguments for the validity of
our comparison axiom are given by considering the limiting behavior of the
self-force on extended bodies.Comment: 37 pages, LaTeX with style package RevTeX 3.
Axiomatic approach to radiation reaction of scalar point particles in curved spacetime
Several different methods have recently been proposed for calculating the
motion of a point particle coupled to a linearized gravitational field on a
curved background. These proposals are motivated by the hope that the point
particle system will accurately model certain astrophysical systems which are
promising candidates for observation by the new generation of gravitational
wave detectors. Because of its mathematical simplicity, the analogous system
consisting of a point particle coupled to a scalar field provides a useful
context in which to investigate these proposed methods. In this paper, we
generalize the axiomatic approach of Quinn and Wald in order to produce a
general expression for the self force on a point particle coupled to a scalar
field following an arbitrary trajectory on a curved background. Our equation
includes the leading order effects of the particle's own fields, commonly
referred to as ``self force'' or ``radiation reaction'' effects. We then
explore the equations of motion which follow from this expression in the
absence of non-scalar forces.Comment: 17 pages, 1 figur
Does Quantum Mechanics Clash with the Equivalence Principle - and Does it Matter?
With an eye on developing a quantum theory of gravity, many physicists have
recently searched for quantum challenges to the equivalence principle of
general relativity. However, as historians and philosophers of science are well
aware, the principle of equivalence is not so clear. When clarified, we think
quantum tests of the equivalence principle won't yield much. The problem is
that the clash/not-clash is either already evident or guaranteed not to exist.
Nonetheless, this work does help teach us what it means for a theory to be
geometric.Comment: 12 page
Combined Effect of Dietary Cadmium and Benzo(a)pyrene on Metallothionein Induction and Apoptosis in the Liver and Kidneys of Bank Voles
Bank voles free living in a contaminated environment have been shown to be more sensitive to cadmium (Cd) toxicity than the rodents exposed to Cd under laboratory conditions. The objective of this study was to find out whether benzo(a)pyrene (BaP), a common environmental co-contaminant, increases Cd toxicity through inhibition of metallothionein (MT) synthesisâa low molecular weight protein that is considered to be primary intracellular component of the protective mechanism. For 6Â weeks, the female bank voles were provided with diet containing Cd [less than 0.1Â ÎŒg/g (control) and 60Â ÎŒg/g dry wt.] and BaP (0, 5, and 10Â ÎŒg/g dry wt.) alone or in combination. At the end of exposure period, apoptosis and analyses of MT, Cd, and zinc (Zn) in the liver and kidneys were carried out. Dietary BaP 5Â ÎŒg/g did not affect but BaP 10Â ÎŒg/g potentiated rather than inhibited induction of hepatic and renal MT by Cd, and diminished Cd-induced apoptosis in both organs. The hepatic and renal Zn followed a pattern similar to that of MT, attaining the highest level in the Cdâ+âBaP 10-ÎŒg/g group. These data indicate that dietary BaP attenuates rather than exacerbates Cd toxicity in bank voles, probably by potentiating MT synthesis and increasing Zn concentration in the liver and kidneys
Spin and quadrupole contributions to the motion of astrophysical binaries
Compact objects in general relativity approximately move along geodesics of
spacetime. It is shown that the corrections to geodesic motion due to spin
(dipole), quadrupole, and higher multipoles can be modeled by an extension of
the point mass action. The quadrupole contributions are discussed in detail for
astrophysical objects like neutron stars or black holes. Implications for
binaries are analyzed for a small mass ratio situation. There quadrupole
effects can encode information about the internal structure of the compact
object, e.g., in principle they allow a distinction between black holes and
neutron stars, and also different equations of state for the latter.
Furthermore, a connection between the relativistic oscillation modes of the
object and a dynamical quadrupole evolution is established.Comment: 43 pages. Proceedings of the 524. WE-Heraeus-Seminar "Equations of
Motion in Relativistic Gravity". v2: fixed reference. v3: corrected typos in
eqs. (1), (57), (85
Effect of dietary cadmium and/or lead on histopathological changes in the kidneys and liver of bank voles Myodes glareolus kept in different group densities
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